The United States is "lurching toward a period of uncertainty and increased risk" in this election year and during the upcoming presidential transition, according to a new Congressional Research Service study that suggests counterterrorism responses that Congress, the Bush administration and its potential successors could take.

The report, released Monday, noted that new security officials and agencies put in place after the Sept. 11, 2001, terrorist attacks -- such as the Office of the Director of National Intelligence, the National Counterterrorism Center and the Department of Homeland Security -- will soon undergo their first presidential handoff.

It quoted experts cautioning that the administration is focusing too much on administrative tasks for the transition and not enough on preparing its successors for likely security challenges. More work needs to be done with state and local officials, including contingency planning for any election disruption or incident, to which they would lead responses, the report said.

"What training or exercises are underway to test our new roles and responsibilities if an event were to occur?" Rep. Bob Etheridge (D-N.C.) asked in a hearing Wednesday led by House Homeland Security Committee Chairman Bennie G. Thompson (D-Miss.), where Democrats threatened to subpoena DHS to produce detailed information about its plans.

Homeland Security Secretary Michael Chertoff acknowledged recent attempts to disrupt political transfers of power in other countries, citing the Madrid train bombings in March 2004, before national elections in Spain.

However, he added in a session with Washington Post reporters and editors recently, "I worry less about that as a trigger than I am concerned about the fact . . . that terrorists might presume we would be distracted -- that people who are in the job might be looking at what they are going to do next, and that there won't be new people coming in."

Chertoff has said he would like to encourage the next president's homeland security aides to "participate in a tabletop exercise" before taking office.

In preparation for the transition, DHS held a three-day conference and exercise in February and plans another next month for top career officials; is setting up an electronic records management system; and will prepare a formal plan by October, senior officials have said.

The department also has increased its ranks of high-level career officials, reordered its chain of succession and engaged outside advisers, its leaders said. It has identified career officials to serve as interim leaders in about 25 key positions if necessary. For example, the Federal Emergency Management Agency has named Region IX chief Nancy Ward, a career official based in Oakland, Calif., to head the department until the next president's choice is sworn in.

Under scrutiny by Congress, the White House and security analysts, DHS also is developing transition plans with the Council for Excellence in Government and the National Academy of Public Administration. It plans to test communication lines with other federal and nonfederal agencies; identify the best transition practices of state, local and private entities; and draft transition handbooks and briefing materials.

Congressional analysts said other domestic-security-related agencies are lagging behind DHS in preparing for the transition. The report suggested, for example, that the White House create an expert group from the National Security and Homeland Security councils to discuss transition issues.

It praised a January report by a DHS advisory council that identified the 30 days before Election Day through the first six months of the next president's term as "the most vulnerable period," and it noted calls for closer collaboration with aides to Sen. John McCain (R-Ariz.) and Sens. Hillary Rodham Clinton (D-N.Y.) or Barack Obama (D-Ill.).

Chertoff cited the importance of quick confirmations of national security appointees, noting that FBI Director Robert S. Mueller III was sworn into office just one week before the Sept. 11 attacks. At the time, only 227 of 508 top Bush administration political positions were filled, and 106 people had been on the job for less than eight weeks, according to a 2002 study.

"We can't afford to let that happen again," Chertoff said.

In fact, Congress in 2004 vowed to give speedy consideration to national security nominees submitted by the next president by Inauguration Day, saying it would try to vote on them within 30 days.